Clinical manifestation of overt vascular disease may be preceded for years by endothelial dysfunction. Objective: This study was undertaken to evaluate endothelial function in ESRD patients and correlation between endothelial function and clinical and biochemical parameters. Methods: 32 stable ESRD patients (male : female = 16 : 16, average age: 55.2 ± 13.0) on hemodialysis were included. A 10-MHz ultrasound transducer was used to image the brachial artery. Brachial artery diameter was measured, and reactive hyperemia was induced by inflation to 250 mmHg for 5 min and then deflation of a pneumatic cuff. After release of the cuff, brachial artery diameter was measured. Results: In the entire study population and non-diabetic group, the %FMD (% flow-mediated dilatation, % change of brachial artery diameter between before and after cuff inflation) did not show any significant correlation with duration of dialysis, age, hypertension, albumin, CRP, total cholesterol, LDL and HDL cholesterol, and triglyceride. However, the %FMD of diabetic patients was lower than that of non-diabetics. Among the patients with diabetes, the group of patients with FMD of <5.2% showed significant lower serum albumin and significantly higher ln(CRP) levels compared to the group of patients with FMD ≥5.2%. The %FMD showed significant positive correlation with serum albumin level and significant negative correlation with ln(CRP) in diabetic patients. Conclusion: These findings suggest that endothelial dysfunction, estimated by FMD, was significantly more prominent in diabetic ESRD, especially with low serum albumin and high CRP levels.